Printing apparatus using porous printing member, reservoir and control means



y 1966 ,L. F. HERTE ETAL 3,252,164

' PRINTING APPARATUS USING POROUS PRINTING MEMBER, RESERVOIR AND CONTROL MEANS Flled April 50, 1964 INVENTORS LAWRENCE F HERTE STANLEY E. SANFORD BY ATT NEY tacts the recording paper.

4 3,252,164 .PRINTING APPARATUS USING POROUS PRINT- ING MEMBER, RESERVOIR AND CONTROL MEANS A Lawrence F. Herte, Palo Alto, and Stanley E. Sanford, Milpitas, Calif., assignors to Varian Associates, Palo Alto, Calif., a corporation'of California Filed Apr. 30, 1964, Ser. No. 363,882 10 Claims. (Cl. 346140) The present invention relates to a printing apparatus of the kind having a porous printing member. While not limited thereto, the invention is particularly useful in recorders for point-plotting a curve in a rapid-predetermined sequence, and in other apparatus employing high speed character printing.

A typical graphic recorder used for continuously scribing, i.e., line-plotting, a curve upon recording paper includes a pen assembly adapted to slide along a bar. The

- bar is positioned transversely to a writing surface upon which recording paper is disposed. In the case of a strip chart graphic recorder the.bar remains stationary and the pen assembly is caused to slide along the bar in response to an electric signal, while the recording paper moves at a steady rate over the writing surface. In the case of an X-Y graphic recorder the recording paper is held on the writing surface and the pen assembly is caused to slide along the bar in response to an electric signal, while the bar moves at a steady rate over the writing surface-or in response to another independent electric signal.

Typically, a pen assembly comprises a holder slidably mounted upon the transversely positioned bar and is adapted to detachably support a recorder pen, The pen includes a writing medium or ink reservoir and a stylus, typically a piece of small diameter metal tubing having one end communicating with the interior of the reservoir and its opposite end turned down to form the scribing point.

The pen assembly is disposed in a raised, non-writing position with respect to the recording paper until an electric signal initiates movement of the pen assembly, or both pen assembly and transverse bar in the case of an X-Y graphic recorder. The pen assembly is lowered into a writing position in which the tip of the stylus con- A steady flow of ink from the reservoir to the tip of the stylus allows a curve to be continuously scribed upon the recording paper.

Such prior art recorder pens have generally been found to be satisfactory when used for continuously scribing,

i.e., line-plotting, a curve, although not without some inherent problems. For example, if the diameter of the pen stylus becomes too large the pen will drip ink profusely. Another problem is that when a pen is not used for long periods of time, say overnight, the ink in the stylus dries causing clogging and some of the ink in the reservoir will evaporate, the amount depending on the period of non-use. In attempting to use these pens for point-plotting operations, where a curve is scribed from a series of points continually impressed on the recording paper in a rapid pre-determined sequence, additional difficulties have been encountered of such proportion as to render such pens useless for point-plotting operations. With the continual pulsing of the pen assembly, necessary in point-plotting operation, dripping of ink, not only from the tip of the stylus 'but also from breather apertures in the top of the reservoir, is even more prevalent. Also, when the tip of the stylus is brought into contact with the recording paper it sets down an excessive amount of ink in the form of a thick droplet which does not dry even over long periods of time.

It is the object of the present invention to provide a v United States Patent l Patented May 17, 1966 See novel printing apparatus of the kind having a porous printing member, which, while not limited thereto is useful in recorders and other apparatus employing high speed character printing.

Briefly stated, in accordance with the teachings of the present invention a printing apparatus is constructed which includes, a chamber or reservoir for containing a printing medium such as ink, a porous printing member such as a porous metal rod one end of which has an impression forming surface or type face and the other end of which extends into the reservoir, and a means for controlling the flow of the printing medium from the reservoir and through the printing member to the impression forming surface of the printing member.

The printing member is made of a suitable absorbent material, preferably of a metallic nature, having a microreticulated structure. By a microreticulated structure is meant a rigid solid material having an inter-connected network of open spaces or pores of microscopic proportions. The printing medium or ink is transferred by capillary action alone, or by capillary action and gravityfeed from the chamber or reservoir through the printing member or rod to the impression forming surface or type face of the rod. Ink does not leave the type face until its surface tension and adhesive attraction to the type face is broken, for example, by touching the paper. The ink removed is immediately replaced by ink from the reservoir and that ink volume is replaced by expansion of air left in the reservoir. The lowered air pressure in the reservoir or well provides a deterrent against dripping of ink from the type face.

The amount of ink delivered to the type face is dependent on, among other things, properties of the porous rod and the characteristics of the ink. The present invention contemplates a means for controlling the flow of ink from the reservoir and through the porous rod to the type face of the rod. In a preferred embodiment this means takes the form of a precision breather tube leading into the reservoir, the end of which is submerged in the ink. When the air pressure within the reservoir becomes sufiiciently low, a bubble of air is drawn in from the atmosphere through the submerged breather tube and percolates through the ink. In an alternate'embodiment the porous rod extends through the reservoir so that when ink is removed from the type face its volume is replaced by air drawn in through a porous portion of the rod below the level of ink in the reservoir.

One feature of the present invention is the. provision in a printing apparatus of means for controlling flow of a printing medium from a chamber or reservoir through a porous printing member to an impression forming surface of said member.

Another feature of the present invention is the provision of control means of the above kind which includes means for conducting replacement air from the exterior of said reservoir to its interior through said printing medium.

Still another feature of the present invention is the provision of means for conducting replacement air from the exterior of said reservoir to the interior through said printing medium wherein said conducting means comprises a breather tube.

A further feature of the'present invention is the provision of means for conducting replacement air from the exterior of said reservoir to its interior through said printing medium wherein said conducting means is a porous member which may be integral with said porous printing member. I

A still further feature of the present invention is the provision in a printing apparatus of the above kind of an elongated porous printing member having both vertical and horizontal segments whereby said printing apparatus may be used on both horizontally and vertically disposed impression receiving surfaces.

These and other objects and features of the present invention and a further understanding may be had by referring to the following description and claims, taken in conjunction with the following drawing in which:

FIG. 1 is a perspective view partially broken away of an X-Y graphic recorder utilizing the novel printing apparatus of the present invention in the form of a recorder pen;

FIG. 2 is an enlarged fragmentary plan view of the pen holder and novel pen shown in FIG. 1;

FIG. 3 is a view taken along the lines 3-3 of FIG. 2 partially broken away; i

FIG. 4 is an enlarged cross-sectional view taken along the lines 4--4 of FIG. 3;

FIG. 5 is an enlarged cross-sectional view of an alternate embodiment of the novel pen of the present invention; and,

FIG. 6 is a front view partially broken away of still another embodiment of the novel pen of the present invention.

Referring now to FIGS. 1 and 2 there is shown an X-Y graphic recorder 11 upon which a pen assembly 12 is mounted. The pen assembly 12 includes holder 13 and a printing apparatus or pen 14. .The pen 14 includes a reservoir 15 and a printing member or rod 16 suitable for scribing a curve 17 upon an impression forming surface or recording paper 18 held on the writing surface 19 of the recorder 11. The pen holder 13 is mounted upon and adapted to move along a Y-axial bar 20 positioned transversely to the writing surface 19. The bar 20 is joined to X-axial side carriages 21 which are movable by means of cords-and pulleys (not shown) which produce movement along the X axis. Movement of pen holder 13 along the Y axis likewise may be produced as a result of tension exerted by means of a servo motor (not shown) upon cords 22 attached to pulleys 23 mounted upon pen holder 13.

The pen holder 13 may include a magnetic strip 24 cemented to the central portion of holder 13. The pen 14 may have a steel plate connective member 25 including lips (not shown) adapted to fit in interlocking fashion within grooved portions 26 of holder 13. Thus, pen 14 may be detachably held in interlocking fashion to holder 13 due to the magnetic affinity of strip 24 for connective member 25. A more detailed description of pen holder 13 and related apparatus may be had by reference to U.S. Patent application Serial No. 298,051, filed July 29, 1963 and assigned to the same assignee as the present invention.

Referring now to FIGS. 2-4, pen 14 has a reservoir 15 i for containing a printing medium or ink 27 and a printing member or rod 16. A means 28 is provided for controlling the flow of ink 27 through the rod 16 to the impression forming surface 29 of rod 16.

The reservoir 15 may be made of a translucent material such as acrylic (methyl methacrylate) resin (Lucite) or a clear styrene, and typically is approximately F7 l0ng,, at its greatest width, and at its greatest depth. Ink is introduced into the reservoir 15 through a port 30 in top plate 31, which at all other times is cov-,

eved by a closure member 32.

The rod-like printing member 16 is mounted so as to extend through an opening 33 in the base of reservoir 15 and also through a seal 34 which extends through opening 33 and is secured between rod 16 and the base of reservoir 15 so as to prevent leakage of ink 27. Rod 16 extends upwardly through the ink 27 and terminates in a resilient cylindrical grommet 35, for example, silicone rubber, held within a support bracket 36 and sealed to top plate 31. The lower portion of rod 16 terminates in an impression forming surface 29, in the embodiment depicted, the letter O.

The rod is made of a suitable microreticulated material, preferably metallic, having sufficient porosity to permit the upper portion of rod 16 to absorb ink 27 and transfer it to the impression forming surface 29, when needed, by capillary action alone, or by capillary action and gravity-feed and without the necessity of additional pumping mechanism. On the other hand, the pores must not be so large as to permit dripping of ink from the impression forming surface 29 at any time. The rod must also have sufficient rigidity to maintain its form as it is reciprocated and caused to contact the recording paper 18. A material suitable for this purpose is 440 C stainless steel manufactured by Mott Metallurgical Corporation of 272 Huyshope Avenue, Hartford, Connecticut. The pore size range should be from 2 microns or slightly less but in no event greater than 10 microns, the pore density being about 50% by volume. Below this size range a constant flow to the impression forming surface may not be maintained without additional means for causing positive flow. Above this range ink drips profusely. Typically, the rod is /6" long having a diameter of .067". In the embodiment depicted the impression forming surface 29 is .035" deep and the inner diameter is .030".

It is not necessary that the exterior of the non-impression forming surfaces of rod 16 external of reservoir 15 be coated or otherwise made non-porous so as to prevent leakage or dripping of ink onto the paper 18 or adjacent surfaces of pen 14 since ink does not leave the rod until a portionof it is brought into contact with the recording paper 18. However, in the embodiment depicted, due to the coating action of the material used for the seal, typically, silicone rubber, the outer pores of the external portion of rod 16 become non-porous except for the impression forming surface 29.

The ink 27 is preferably one, which dries rapidly once it is impressed on the recording paper 18, whose viscosity is such as to permit transfer of the ink through the porous rod 16 yet has the least tendency to drip under any conditions, which contains a fungicide to retard bacterial growth within the reservoir 15 and which makes a clear, legible impression. Water base Esterbrook type CMI has been found to be satisfactory.

In accordance with the present invention a means 28 is provided for controlling the flow of ink from the reservoir 15 to the impression forming surface 29. In the preferred embodiment disclosed this means 28 takes the form of a precision diameter breather tube allowing air to replace metered-out ink. The tube 28 is substantially enclosed within reservoir 15, has its tip 37 extending through an opening 38 in top plate 31. The lower end 39 of tube 28 is submerged in the ink 27 in reservoir 15. If lower end 39 is not submerged, proper regulation of the minute quantities of the ink involved may not be attained and too much ink will flow. Also, the ink supply will evaporate more rapidly. On the other hand, if no tube 28 is provided at all, no regulation is attainable. Moreover the printing means 16 will write only for a limited period of time as the lowered air pressure within reservoir 15 will have the tendency to retard flow of ink to the surface 29. The tube 28 may consist of stainless steel needle tubing .006" inside diameter or of a flexible plastic material such as tetrafluoroethylene (Teflon), for example, having an inside diameter of .025 where the diameter of the opening in the tip 37 is preferably on the order of .003".

A pen as described above has been constructed and used in a recorder of the above kind for point-plotting operation, although it has been found to be completely satisfactory for line-plotting operation as well. The pen assembly 12 was pulsed by solenoid control means (not shown) to make twenty (20) clear and legible impressions or plots per second with a striking force as low as 5 grams. Impact time, that is, the time in which the impression forming surface 29 is in contact with the less than 50 milliseconds.

recording paper 18, was on the order of 5-10 milliseconds and recovery time, that is, the time to replace the ink transferred from the impression forming surface 29 to the recording paper on the last plotting operation, was No dripping ever occurred and the pen did not clog even after long periods of nonuse. When the supply of ink 27, typically two (2) cubic centimeters, was consumed the pen was immediately reactivated upon addition of more ink. No evaporation was observed.

Referring now to FIG; 5 there is shown an alternate embodiment of the present invention which includes a reservoir 40 for containing a printing medium or ink 27 and a porous printing member or rod 41. The rodlike printing member 41 is mounted so as to extend through an opening 42 and also through a seal 43, which seal extends through the opening 42 and is secured between rod 41 and the base of reservoir 40. Rod 41 extends upwardly through the ink 27, through an opening 44 in the top plate 45 and also through a seal 46, which seal extends through opening 44 and is secured between rod 41 and top plate 45. The lower portion of rod 41 terminates in an impression forming surface 47. The rod is made of 'a suitable porous material as previously described. The outer pores of the external portion of rod 41 below reservoir 40 are non-porous except for the impression forming surface 47. The portion of the rod within the reservoir 40 is coated or otherwise made nonporous except for a small portion near the base of reservoir 40.. The portion of rod .41 above reservoir 40' is porous.

In this embodiment the rod 41 acts both as the printing member and as the means for controlling the flow of ink from the reservoir through the rod 41 to the impression forming surface 47. Replacement air is conducted into the reservoir 40 and through the ink 27 by means of the porous rod 41 itself.

In some applications it is desirable to place the recorder 11 in certain vertical positions such as might be found by mounting the recorder 11 in a vertical rack mount (not shown). I

Referring now to FIG. 6 there is shown still another embodiment of the present invention in which the porous printing member 48 includes both a vertical segment 49 and a horizontal segment 50. As long as the level of the ink 27 is sufiicient that a portion of either vertical segment 49 or horizontal segment 5d and the lower end 39 of tube 28 remain submerged, ink 27 will flow from reservoir to the impression forming surface 51 of printing member 48. The embodiment disclosed in FIG. 6, therefore, is advantageously adapted for writing upon recording paper which may be oriented in a horizontal plane or in one or more vertical planes as may be required, in various applications.

The novelprinting apparatus of the present invention has been described in a preferred embodiment as the pen of a recorder. It should be readily apparent, however, that the apparatus would have utility in numerous other printing applications, particularly where high speed impact printing is involved. For example, the teachings of the present invention could be used to advantage in rotary type-wheels in which the entire structure would be made of a porous metal material as described above. It would be advisable in this application to coat the external non-impression forming surfaces so as to reduce evaporation. It may also be used in multiple character imprinting, magnetic check imprinting, numbering machines, credit card imprinting, postage meters and the like. Since many changes can be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A printing apparatus comprising: an enclosed, evacuatable chamber for holding a printing medium; a rigid, reusable, microreticulated member having a first portion in fluid communication with the interior of said chamber and a second portion located exteriorly of said chamber having an impression forming surface'thereon for imprinting indicia; and means for controlling the flow of printing medium from said chamber through said member to said impression forming surface, said control means including means forconducting replacement air to the interior of said chamber through said printing medium in response to the withdrawal of printing medium from said impression forming surface.

2. The apparatus according to claim 1 wherein said conducting means comprises a breather tube having one end open to the atmosphere and an opposite end immersed in said printing medium.

3. The apparatus according to claim 1 wherein said conducting means comprises a member having one portion open to the atmosphere and a second portion immersed in said printing medium, said conducting member having a rigid, microreticulated interior. I

4. In a printing apparatus having an enclosed, evacuatable chamber for holding a printing medium, a porous member having a first portion in fluid communication with the interior of said chamber and a second portion located exteriorly of said chamber having an impression forming surface thereon for imprinting indicia and means for controlling the flow of printing medium to said impression forming surface, the improvement that said porous member is constructed of rigid, reusable, micro-reticulated material and that said control means comprises means for conducting replacement air to the interior of said chamber through said printing medium in response to the withdrawal of printing medium from said impression forming surface.

5. The improvement according to claim 4 wherein said conducting means comprises a breather tube having one end open to the atmosphere and an opposite end immersed in said printing medium.

6. The improvement according to claim 4 wherein said conducting means comprises a member having'one portion open to the atmosphere and a second portion immersed in said printing medium, said conducting mem ber having a rigid, microreticulated interior.

7. The improvement according to claim 6 wherein said porous member has elongated segments within said chamber at angles with respect to one another.

8. A printing apparatus comprising: an enclosed evacuatable chamber for holding a printing medium having a first and second walled portion; a rigid, reusable, microreticulated rod-like member extending through said second walled portion having a first end located within said chamber, resiliently held spaced from said first Walled portion and a second end located exteriorly of said chamber having an impression forming surface thereon for imprinting indicia; and means for controlling the flow of printing medium from said chamber through said member to said impression forming surface, said control means comprising a breather tube mounted in said first walled portion having one end open to the atmosphere and an opposite end immersed in said printing medium for conducting replacement air to the interior of said chamber through said printing medium in response to the withdrawal of printing medium from said impression forming surface.

9. The apparatus according to claim 8 including an elongated, rigid, reusable microreticulated segment integral with and approximately at a right angle to,said rod-like member. j

10. A printing apparatus comprising: an enclosed, evacuatable chamber for holding a printing medium having a top and a bottom walled portion; a rigid, reusable, microreticulated rod-like member sealed to said 7 top and bottom walled portions and extending completely through said chamber, the surface of said member within said chamber being non-porous from the top walled portion to just above said bottom walled portion, said member having a bottom end portion located exteriorly of said chamber below said bottom Walled portion with an impression forming surface thereon for imprinting indicia, and a top end portion located exteriorly of said chamber above said top walled portion for conducting replacement air to the interior of 10 3,019,072

said chamber through said printing medium in response to the withdrawal of printing medium from said impression forming surface.

References Cited by the Examiner UNITED STATES PATENTS Mekren 346-440 Hall 346-140 Lovejoy 346--140 Walker 346+62 Rost 346-140 X Brown 101327 Boss et a1. 346-29 LEO SMILOW, Primary Examiner. 

1. A PRINTING APPARATUS COMPRISING: AN ENCLOSED, EVACUATABLE CHAMBER FOR HOLDING A PRINTING MEDIUM; A RIGID, REUSABLE, MICRORETICULATED MEMBER HAVING A FIRST PORTION IN FLUID COMMUNICATION WITH THE INTERIOR OF SAID CHAMBER AND A SECOND PORTION LOCATED EXTERIORLY OF SAID CHAMBER HAVING AN IMPRESSION FORMING SURFACE THEREON FOR IMPRINTING INDICIA; AND MEANS FOR CONTROLLING THE FLOW OF PRINTING MEDIUM FROM SAID CHAMBER THROUGH SAID MEMBER TO SAID IMPRESSION FORMING SURFACE, SAID CONTROL MEANS INCLUDING MEANS FOR CONDUCTING REPLACEMENT AIR TO THE INTERIOR OF SAID CHAMBER THROUGH SAID PRINTING MEDIUM IN RESPONSE TO THE WITHDRAWAL OF PRINTING MEDIUM FROM SAID IMPRESSION FORMING SURFACE. 